Process for simultaneously increasing recovery and upgrading oil in a reservoir

ABSTRACT

A process for simultaneously increasing recovery and upgrading oil in a reservoir by injecting gas produced by the in situ gasification of coal to increase recovery and upgrade said oil. The gas is also useful in the production of steam and other gaseous materials for injection.

United States Patent Young et al.

45] May 7, 1974 [5 1 PROCESS FOR SIMULTANEOUSLY INCREASING RECOVERY ANDUPGRADING 01L IN A RESERVOIR [75] Inventors: Gary C. Young; Howard H.Ferrell,

both Of POnca City, Okla.

[73] Assignee: Continental Oil Company, Ponca City, Okla.

22 Filed: Oct. 2, 1972 21 Appl. No.5 293,968

[52] US. Cl. 166/258, 1 66/272 [51] Int. Cl E2lb 43/14, E2lb 43/24 [58]Field of Search 166/256, 258, 260, 261,

[56] References Cited UNITED STATES PATENTS 8/1971 Messman et a1.166/258 2/1952 Merriam et a]. 166/258 2,695,163 11/1954 I 3,010,70711/1961 Craighead et a1 166/258 3,044,545 7/1962 Tooke 166/261 3,294,16712/1966 Vogel 166/272 3,344,856 10/1967 Lange 166/266 3,360,044 12/1967Lange 166/272 3,380,913 4/1968 Henderson. 166/267 3,734,184 5/1973 Scott166/261 Primary Examiner-Henry C. Sutherland Assistant Examiner-1ack E.Ebel Attorney, Agent, or Firm-F. Lindsey Scott [57 ABSTRACT A processfor simultaneously increasing recovery and upgrading oil in a reservoirby injecting gas produced by the in situ gasification of Coal toincrease recovery and upgrade said Oil. The gas is also useful in theproduction of steam and other gaseous materials for injection. I

4 Claims, 3 Drawing Figures Pearle er al 166/266 PATENTEDMAY 1 m SHEEIEUF3 PROCESS FOR SIMULTANEOUSLY INCREASING RECOVERY AND UPGRADING OILINA RESERVOIR FIELD OF THE INVENTION DESCRIPTION OF THE PRIOR ARTNumerous processes and methods are known for the gasification of coal toproduce light hydrocarbons, carbon monoxide, carbon dioxide, hydrogenand the like. The use of gas injection as a primary,secondary, ortertiary recovery'method is also known and a typical application of suchtechniques is shown in U.S. Pat. No. 2,734,578 issued Feb. 14, 1966 toWalter. A technique for gasifying oil-bearing shale sands and injectingthe gas so produced to improve secondary oil recovery is shown in U.S.Pat. No. 3,040,809 issued June 26, 1962 to Pelzer. Other referencesconsidered in a prior art search on the concept of the present inventionare: U.S. Pat. No. 1,978,655, issued Oct. 30, 1934 to Straight; U.S.Pat. No. 2,173,556, issued Sept. 19, 1939 -to Hixon; U.S. Pat. No.3,572,436, issued Mar. 30, 1971 1 to Rich]; U.S. Pat. No. 3,548,938issued Dec. 22, 1970 to Parker; U.S. Pat. No. 3,459,265 issued Aug. 5,1969, to Buxton et al.; U.S. Pat. No. 3,208,514 issued Oct. 31, 1962, toDew et al.; U.S. Pat.No. 3,399,721 issued Sept. 3, 1968, to Strange;U.S. Pat. No. 3,480,082 issued Nov. 25, 1969 to Gilliland; U.S. Pat. No.3,360,044 issued Dec. 26, 1967 to Lange; U.S. Pat. No. 3,386,508 issuedJune 4, 1968 to Bielstein et al.; U.S. Pat. No. 2,813,583 issued Nov.19, 1957 to Marx et aL; and U.S. Pat. No. 3,500,913 issued to Nordgrenet al. The references are considered further illustrative of the stateof the art.'

Prior attempts at the use of gas for secondary recovery have beenlimited by the difficulty and expense in obtaining the gas at the siteof the secondary recovery operation. By their nature, such recoverytechniques require that the injected materials must be available atrelatively low expense and in relatively large quantities to allowsuccessful gas injection process operations. As a result much time andeffort has been directed to methods which do not suffer the shortcomingsof the methods disclosed above.

OBJECTS or THE INVENTION transporting the gas substantial distances tothe injection site. 7

SUMMARY OF THE INVENTION It has now been found that the object of thepresent invention is realized in a process for increasing recoveryandupgrading heavycrude oil in a reservoir comprising producing a gaseousmixture by in situ gasification of neighboring coal deposits; injectingthe gaseous mixture into oil reserviors to increase recovery of andupgrade the oils in said reservoir and recovering said oil. The gaseousmixture is also used to generate steam and other gaseous injectionmaterials.

DESCRIPTION or THE DRAWING FIG. 1 is a sketch of the Continental UnitedStates showing selected oil fields and coal fields and the areas inwhich said coal fields neighbor said oil fields.

FIG. 2 is a sketch of a typical embodiment of the present invention.

FIG. 3 is a sketch of an embodiment of the present invention wherein thecoal deposit overlies the oil formation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In primary, secondary andtertiary recovery operations for the recovery of crude oils, it has longbeen known that numerous process utilizing gas injection are useful forsuch recoveries. The primary difficulty in the use of such techniques isthat it oftentimes is difficult to provide large volumes of gaseousmaterial at the oilfield to be treated. The primary difficulties areeconomic as well as the simple handling difficulties in transferringlarge volumes of gas to remote areas.

It has been observed that, as shown in FIG. 1, in many areas in theContinental United States oil fields are located adjacent to coaldeposits. It has now been discovered that an effective and efficientmethod for air has been shown to increase the BTU value of the producedgas. I

The oil recovery process may be selectedfrom a variety of known methods,such as drive processes, steam drive processes, huff and puff processes,and the like. The drive methods typically consist of the injection ofgases, liquids and the like at one well in a formation and the recoveryof gas, condensed gas, liquids, oil and the like at a second well in thesame formation. Steam drive processes are similar withthe majordifferences being that steamis used as the injection gas rather thanother gases and latentheat istransferred to the formation. fHuff andpuff" operations are well known in the art and typically comprise theinjection of steam, heated gasesand the like following which the well issealed and time is allowed for the heat to permeate the formation,following which thewellis reopened and oil is produced from saidwell. Noparticular novelty is claimed in the method for secondary, tertiary orprimary recovery of oil, but rather, the present invention comprises amethod whereby in situ gasification of coal may be utilized to provideareadily available source of gaseous injection materials for oilrecovery 7 techniques requiringan injection gas material.

FIG. 1 is a sketch of the Continental United States showing selected oilfields and coal fields and the areas in which said coal fields neighborsaid coalfields FIG. 2 discloses an embodiment of the present inventionwherein a gas drive process is used. Air is introduced through line 20,line 24, and well 3 into coal deposit 4. The gas produced by thegasification of coal deposit 4 is produced through well 5 and line 26.The gas is then passed through line 26, to well 6 and through well 6into oil formation 7. The gas flow in oil formation 7 is from-well 6 towell 8 and oil and gas are produced through well 8 and line 28. Theoil-gas mixture so recovered is passed to oil recovery where the streamis separated into its respective components, i.e., gas, water and oil.

As will be obvious to those skilled in the art, the injection gas may beignited at the base of well 6 to generate heat in oil formation 7, thusaiding the oil recovery operation. The ignition of the gas at the baseof well 6 may be conducted in such a manner that well 6 is completelycoked in as is well known to those skilled in the art. Numerous othermodifications and variations of the gas drive process are possible andmay be readily apparent to those skilled in the art upon review of theforegoing description. It will, of course, be noted that water may besupplied through lines 22 and 24 to coal deposit 4. As notedhereinbefore, the produced gas has a higher BTU content in manyinstances when water is injected with the air. It will, of course, beunderstood that air is used to generally include any oxygencontaininggas such as air, oxygen enriched air, and the like.

The produced gas may optionally be used to generate steam which may beinjected into oil formation 7. The steam is generated by combustion ofthe gas produced by the gasification of the coal in conventional steamboilers and the like. The generated steam is then passed to oilformation 7 and the oil recovery is conducted in a manner similar tothat described above wherein the gas from the coal gasification is used.As will be obvious tothose skilled in the art, many variations andmodifications of the above procedures are possible, for instance, watermay be introduced into oil formation 7 with the produced, gas, with thesteam and the like.

Steam may be added with the gas produced by the gasification of .thecoal so that the injection gas at the bottom of well 6 may be gasproduced by gasification of coal, a combination of steam and the gasproduced by gasification of coal, or either of the streams may be usedin conjunction with water, and the like.

FIG. 3 discloses a preferred embodiment of the present invention whereinthe coal deposit overlies the oil formation. Air, oxygen enriched air,or an oxygencontaining stream mixed with water, is produced byintroducing air and the like through line 22 and water through line 24into line 20 for injection into well 1 and well 3. The injection gas isthen passed into coal deposit 4 to produce producer gas by thegasification of coal deposit 4. The flow of the oxygen containinggaseous mixture is shown by arrows 30 and the producer gas flow is shownby arrows 36. The producer gas flows down the bore of well 2 and throughoil formation 7 thus resulting in the production of oil and producer gasthrough wells 1 and 3. The producer gas and oil flow are shown by arrows40.

The oil-gas mixture is then produced from wells 1 and 3 through lines 26and 28, and passed to oil and gas recovery. The combustion of the coaldeposit is in a reverse direction to the flow of the injection gas. Thecombustion front 32 is shown by arrows 34 to move in a directionopposite the flow of the oxygen-containing gas which flows as shown byarrows 30.

In a variation of the above-described method the burn rate in the coaldeposit may be reduced to a minimum and the well closed in for aperiod'of time to allow the heat to permeate oil formation 7. After theheat has permeated oil formation 7, well 2 is opened and produced. Thisoperation is similar to a buff and puff operation in the sense that theheated gaseous mixture is injected into oil formation 7, allowed topermeate the formation, and thereafter oil is produced at intermittentintervals. It should also be noted that when shale layer 17 isrelatively'thin, heat from the gasification of the coal deposit 4 willbe transmitted to oil formation 7, thus further aiding recovery. Manyvariations and modifications of the foreging procedures are possible andmay be obvious to those skilled in the art. Such modifications areconsidered within the scope of the present invention and as heretoforenoted the primary novelty in the present invention lies in thegasification of neighboring coal deposits to provide an economical andreadily available source of gaseious mixtures for primary, secondary,and'tertiary oil recovery operations.

The particular method for the gasification of coal is of no particularimportance to the process of the present invention so long as a productgas comprising from about 15 to about 60 mole percent carbon dioxide,from about I to about 10 mole percent methane, from about 0.0 to about0.4 mole percent oxygen, from about 5 to about 60 mole percent hydrogen,from about 2 to about 51 mole percent carbon monoxide, from about 10 toabout 80 mole percent nitrogen, and from about 0.1 to about 30 moles ofwater per mole of dry gas is produced. Such gases are useful in theprocess of the present invention although a preferred gas composition isfrom about 10 to about 36 mole percent carbon dioxide, from about 2.0 toabout 7.6 mole percent methane, from about 0.3 to about 0.4 mole percentoxygen, from about 10 to about 50 mole percent hydrogen, from about 10to about 15 mole percent carbon monoxide, from about 10 to about molepercent nitrogen, and from about 0.13 to about 2.0 mole of water permole of dry gas.

It will be further recognized by those skilled in the art that wells maybe coked to the point of consolidating unconsolidated formations bysimply combusting the gas mixture at the bottom of the well. Such is notconsidered the primary objective of the present invention and normallygas would be injected and sealed in to allow recovery of oil cyclicallyor gas would be injected continuously and oil recovered continuously.

As shown in FIG. 1, in numerous areas in the Continental UnitedStates,coal deposits neighbor oil fields. This situation makes it possible toutilize the process of the present invention to gasify coil in situ andutilize the gaseous mixture for gas injection recovery techniques withneighboring oil fields. Neighboring as used in the context of thepresent specification refers to coal fields which overlie, underlie, orare near the oil fields to be treated by the gas injection procedures.The use of such neighboring coal and oil fields allows the use of gasproduced in situ to provide a large volumeof low cost gaseous materialat the site of the injection treatment.

Such a process has not been available heretofore. The advantages of sucha processover processes utilizing surface generation of gas, thepipingof gas over long distances, and the like are obvious to those skilled inthe art. A further advantage is that in many situations a low-grade coaldeposit may be utilized to generate the gaseous mixture, therebyutilizing a resource which is not economically useful otherwise.Although it is shown that in the Continental United States, many areasare adapted to the use of the process of the instem invention, it shouldbe understood that the scope of the invention is not so limited and thatany area anywhere in the world having coal deposits neighboring oilfields is adapted to the application of the process of the presentinvention.

The use of the gaseous mixtures described above achieves thermalstimulation of the oil formation, since the injection gas may be hot asproduced or can be readily heated and the carbon dioxide and methane arereadily absorbed by the crude oils, thereby reducing the viscosity. Inaddition, it should be pointed out that while applicants wish to bebound by no particular theory, it is believed that the hydrogen in thegaseous mixture reacts catalytically at the sand-crude oil surfaces toreduce the viscosity of the crude oil further, thereby improving thecrude oil quality and increasing recovery. There arethus threemechanisms acting to increase recovery and improve crude oil quality,i.e., thermal stimulation, absorption of light materials by the crudeoil, and hydrogenation of the crude oil. A further advantage is that thehydrogenation of the crude oil tends to reduce the sulfur content of theoil, thereby further improving the product quality. The use of such amixture and a showing of synergistic qualities in improving oil recoveryis shown in U.S. Pat. No. 2,734,578 issued Feb. 14, 1956 to Walter. Thefact that such a mixture has been used heretofore, merely emphasizesfurther the utility of applicants process. Applicants have found anovel, reliable, and economical method for providing such desirablegaseous mixtures at low cost and in large quantities to oil fieldswherein gas injection techniques result in increased oil recovery andupgrade the crude oil products. Many modifications and variations arepossible within the scope of the present invention and in light of theforegoing description of preferred embodiments and the followingexamples, it is expected that those skilled in the art will envisionmany such desirable modifications and process variationsin the presentprocess.

EXAMPLES Example 1 In an embodiment of the present invention as shown inFIG. 2, one million standard cubuc feet per day of air is injected intoignited coal bed 4 through well 3. The coal bed is gasified by the airat combustion temperatures greater than about l,500F and the product gasis removed from the coal bed through well 5 and 6 typically has thefollowing composition:

Mole Carbon Dioxide l 1.0 Oxygen 0.3 llluminants 0.3 Hydrogen CarbonMonoxide 13.0 Methane 3.0 Nitrogen 62.4 Water/Mole Dry Gas 0.1

The heating value of such gas is typically from about 25 to aboutBTU/standard cubic foot (SCF) with an average value being about 100BTU/SCF. The specific gravity'of such gases is approximately 0.9 basedupon the specific gravity of air at standard conditions.

During the coal gasification process the composition of the gas willvary therefore, the heating value will vary somewhere between about 25and about 175 BTU/SCF but averaging about 100 BTU/SCF at an airinjection rate of 1,000,000 SCF per day about 1,000,000 SCF of coal gasper day will be produced.

The coal gas is inejcted into oil formation 7 through well6 and is mixedwith air at the base of well 6. The combustion at the base of well 6generates approximately 100,000,000 BTU/day of heat in the oilformation. This technique is continued for some time and thereafter well6 is placed on production. Assuming that oil is produced 'at the ratioof one barrel of oil per million BTU, then it is seen that the averageoil production in response to thermal stimulation would be about 100barrels of oil per day upon producing well 6. It is noted that 100percent efficiency in the transmission of heat and the like has beenassumed in the present example, whereas in practice lower efficiencieswill be re alized, but since such variations are dependent to a largedegree upon the particular formation, the particular method and thelike, it is not necessary to further define those parameters well knownto those skilled in the art.

Having thus described the invention, we claim: 1. A process forincreasing recovery of crube oil in a reservoir formation comprising:

a. producing a combustible gaseous mixture by in situ gasification ofneighboring coal deposits; b. burning said combustible gaseous mixturethereby producing an injection gas; t c. injecting said injection gasinto said reservoirformation; and v d. recovering crude oil from saidreservoir formation.

2. The process of claim 1 wherein said injection gas is steam.

3. The process of claim 2 wherein said crude oil is re- UNITED STATESPATENT OFFICE CERTIFICATE OF CORRECTIO PATENT NO. 3,809,159

DATED October 2, 1972 v T0 (5) Gary C. Young and Howard H. Ferrell It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 3, line 3, "in which said coal fields neighbor said coal fields"should be "in which said coal fields neighbor said oil fields" Column 4,line 19, "foreging" should be "foregoing" Column 4, line 25, "gaseious"should be "gaseous" 1 Column 5, line 54, "cubuc" should be "cubic"Column 6, line 23, "inejcted" should be "injected" Column 6, line 41,"we claim:" should be "we claim" Signed and Sealed this sixteenth Day ofDecember 1975 [SEAL] A nest:

RUTH C. MASON C. MARSHALL DANN Atlesting Officer 7 CommissionerofParents and Trademarks

1. A process for increasing recovery of crube oil in a reservoirformation comprising: a. producing a combustibLe gaseous mixture by insitu gasification of neighboring coal deposits; b. burning saidcombustible gaseous mixture thereby producing an injection gas; c.injecting said injection gas into said reservoir formation; and d.recovering crude oil from said reservoir formation.
 2. The process ofclaim 1 wherein said injection gas is steam.
 3. The process of claim 2wherein said crude oil is recovered by a ''''drive'''' process.
 4. Theprocess of claim 1 wherein said crude oil is recovered by a ''''huff andpuff'''' type process.